Switched reluctance (SR) machines are widely used for various motor control applications due to its rugged and robust construction. Currently known systems and methods for controlling performance of SR machines use various electrical and/or mechanical parameters associated with the SR machine. Among other parameters, proper determination of the position of the rotor relative to the stator of the SR machine, while at rest or at an otherwise substantially low machine speed, is important to the performance and efficiency of the SR machine. The position information for the SR machine is usually, obtained from a position sensor, often a shaft-mounted encoder or resolver, which adds to cost and complexity of the overall drive system.
Sensorless operation is a key aspect of operation of the SR machine. Sensorless operation is important for various applications due to the need for minimum package size, high reliability and low cost for SR machine driven actuators. Reliable and accurate position sensing for switched reluctance motors is a key step towards developing low-cost, high-performance SR machine drives.
Typical methods of estimating rotor position involve injecting a triangular current pulse into one or more idle phases of the stator. A stator current flowing through the idle phases is then estimated using an observer-based estimation approach. The estimated stator current is compared with an actual stator current to generate an error signal. The error signal is used to compute an estimated position of the rotor and an estimated speed of the rotor. However, typically there is a delay between the actual stator current and the estimated stator current. This may result in a weak error signal i.e. the error signal may not be biased towards one of the positive or negative sides. The weak error signal may cause problems with the convergence of the error signal.
Accordingly, there is a need to provide a method and a system for estimating a position and a speed of the rotor of the SR machine that enables more efficient operation and better performance of the SR machine.